1 Volcanoes have been erupting since shortly after the earth was formed. They are still erupting today. About twenty volcanic eruptions occur each day on earth. Some of these eruptions are quiet. Others are violently explosive. Either way, volcanoes can be very dangerous.2 What are the dangers of volcanic eruptions? Most people think the biggest danger is lava flows. However, lava does not usually injure people or animals. The lava flows slowly. Most anything that moves can get out of its way. But lava can run over houses and roads, causing much destruction.3 Pyroclastic flows are mixtures of hot ash and gas. They are more dangerous than lava flows. Pyroclastic flows can travel very quickly down the slope of a volcano, destroying everything in their path.4 Ash and other tephra from volcanic eruptions can cover a wide area. It can be heavy enough to collapse buildings. It can also destroy plants and trees. Poisonous gases that spew out of volcanoes are very unsafe. Eruptions can also cause giant mudslides. They can even trigger a tsunami, a giant, destructive ocean wave.5 Since 1700, more than 250,000 people have been killed by volcanic activity. Entire towns have been wiped out. Many acres of forests and croplands have been ruined.